Electric telephone



' UNITED STATES PATENT OFFICE.

JAMES I). FREEMAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE HOME TELEPHONECOMPANY, OFILLINOIS.

ELECTRIC TELEPHONE.

SPECIFICATION' for-lacing` part of Letters Patent No. 257,686, dated May9, 18.52.

Application filed July 21, 1881. (No model.)

To all whom it may concern:

Be it known that I, JAMES P. FREEMAN, a citizen of the United States,residing at Chicago, in the county ot Cook and State of 111inois, haveinvented certain new and useful Improvements in Electric Telephones, andI do herebydeclare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertans to make and use the same, reference being hadtothe accompanying drawings, and to the letters or figures of referencemarked thereon, which form a part of this specification.

This invention relates to electric telephones adapted to thetransmission ofarticulate speech by means of electrical waves orimpulses traversing a circuit.

The object ot' my improvement is to obtain a greater permanency ofadjustment of the electrodes.

`T0 this end itcousists mainlyin holding the electrode operated by thediaphragm in contact therewith by magnetic force, said electrode beingattached to the keeper of a permanent magnet with which the keeper is incontact along one edge or line only, so that the keeper can oscillate onthe magnet in unison with the vibrations of the diaphragm.

In order that my invention may be clearly understood, I have illustratedin the annexed drawings and will proceed to di scribe one form thereofwhich I have practically tested and found very eective.

Figure 1 is a front elevation of the door or side of a box to which myinvention is shown as connected. Fig. 2 is a rear elevation of the same.Fig. 3 is an edge view. Fig. 4 is a transverse section on line :v .r ot'Fig. 2. Fig. 5 is a separate view ot' the permanent magnet and itskeeper provided with the electrode to be operated by the diaphragm. 4

The same letters of reference indicate like parts in all the figures.

The door or side A,pret`erably made of hard rubber, is provided with theusual central fiaring depression and orifice, covered on the inside bythe diaphragm B, which may be en-` circled around its periphery by aC-ring of soft rubber, andheld in place by a number of clampingspring-fingers, b b, healing on the rubber ring.

the permanent magnet C, which is in this instance an ordinaryhorseshoemagnet. The magnet is arranged to reach to about theeentral.line of diaphragm with its poles, it being at its neutral end securedto the dloor A by a clamp-bar, c, and a screw, c. A thin piece,c2, isplaced between the door andthe magnet to separate it the proper distancefrom the diaphragm. The. keeper is preferably made flat, as shown, andthe end of the electrode E eX- tending to and touching the center ot'the diaphragm is of such a length that it holds that portion ot' thekeeper to which it is attached separated from the magnet, and onlyrpermits the extreme edge ot' the keeper to remain in contact with themagnet, as clearly shown in Fig. 4. Thus the electrode E is held incontact with the diaphragm by the attraction of the magnet C exerted onthe keeper D, which can oscillate on the magnet in unison with thevibrations of the diaphragm. The force. with which the electrode E ispressed against the diaphragm may be primarily regulated by properadjustment ot' the magnet and keeper to make the instrument more or lesssensitive. When once adjusted' no subsequent adjustments will berequired. In order that the keeper may not slip on the magnet, I providethe latter with shoulders c3 c3, against which that edge of the keeperin Contact with the magnet abuts.

The xed electrodethe carbon button H- is carried in a cup, F', of abridge or cross-bar, F, the ends of which rest on elastic cushionscomposed ot' rubber blocks I, and are secured by screw J passing throughthe rubber blocks into taps or nuts in the door A. In securing thecross-bar by the screws the rubber blocks are compressed, sothat theywill force the crossbar back on looseningthe screws. The crossbar canthus be readily adjusted to bring the carbon button H into properposition with respect to the electrode E.

One pole of the batteryis connected by wire Ll to the cross-bar F, whilethe other pole thereof is preferably connected by the wire K to thediaphragm, though it may be connected by a wire, M, to the magnet Cinstead.

I do not claim broadly the a-pplication of a permanentmagnet forsnpportin g byits keeper one electrode of a telephonie transmitter; butI believe myself tobe th'erst who so combined these parts that theelectrode is held in contact with the diaphragm solely by the magneticattraction exerted on the keeper by the magnet.

Having thus described myinvention, what I claim is 1. The combination,substantially as before set forth;s of' the diaphragm, the fixed permanent magnet, the fiat oscillatory keepe'rin constant contact with saidmagnet, and the electrode carried by the keeper and held in contact withthe diaphragm solely by magnetic attraction exerted on the flat sideofthe keeper.

2. The combination, substantially as before set forth, of the diaphragm,the fixed permanent magnet, the fiat oscillatory keeper in constantcontact with said magnet, the elect-rode carried by the keeper and heldin contact with the diaphragm solely by magnetic attraction exerted onthe flat side of the keeper, and the fixed electrode.

3. The combination, substantially as before set forth, of the diaphragm,the electrode operated thereby, andthe oscillatory keeper, of apermanent magnet carrying said electrode, the fixed electrode, the crossbar supporting said fixed electrode, and the elastic cushions interposedbetween the cross-bar and the door or side to which the cross-bar issecured by screws.

In testimony whereof I affix my signature in presence of two witnesses.

JAMES P. FREEMAN.

Witnesses:

EDWARD C. WALLER, II. B. Pnoss'ER.

